Biochemistry
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Adozelesin (formerly U73975, The Upjohn Co.) is a monofunctional DNA alkylating analogue of the antitumor antibiotic (+)-CC-1065. Adozelesin consists of a cyclopropa[c]pyrrolo[3,2-e]indol-4(5H)-one (CPI) alkylating subunit of (+)-CC-1065 and a indole and benzofurans subunit replacing the more complex pyrroloindole B and C subunits, respectively, of (+)-CC-1065. Previous studies have shown that adozelesin forms a reversible covalent DNA duplex adduct via a reaction between the N3 of adenine and the cyclopropyl of the cyclopropapyrroloindole (CPI) subunit. ⋯ This distortion is the result of strong hydrogen-bonding between the amide linker of the indole and benzofuran subunits, and the carbonyl of a central thymine base and second, weaker, hydrogen bond to the exocyclic NH(2) of the central guanine was also observed. (1)H NMR and rMD also indicate that, to accommodate this hydrogen-bond system, the bound adozelesin is not positioned centrally within the minor groove but pushed toward the modified DNA strand. Previous studies on the dimeric CPI analogue bizelesin have indicated the important role the ureylene linker plays in the DNA binding. This study indicates that a similar situation exists in the reaction of adozelesin with double-stranded DNA and provides a possible explanation into the unpredicted sequence selectivity of these ligands.